Electrodeposition



Aug. 25, 1936. -cz. E. YATEs ELEcTRoDPosITIoN Filed Nov. 50, 1954 wmv]Patented ug. 25, i936 yELECTRODEPOSI'IION Charles E. Yates, Perth Amboy,N. J., assignor to Anaconda Copper Mining Company, New York, N. Y., acorporation of Montana Application November so, 1934, serial No.'155,371

16 Claims.

This invention relates to the eiectrolytic deposition of thin metallicsheets and foils and is concerned more particularly with a novelapparatus by which the production of thin sheets and foils 5 of uniformthickness and without pinholes can be carried on without interruptionfor long periods of time at a high output rate. The new apparatus may beused to special advantage in the manufacture of products of copper andan l embodiment of the invention suitable for that purpose willaccordingly be described in detail for purposes of explanation. It is tobe understood, however, that the utility of the invention is not limitedto the deposition of that particular metal l and it will be apparentthat the new apparatus may be employed for the production of sheets andfoils of various other metals which can be deposited with facility.

The new apparatus includes a rotating drum' cathode on which metal iscontinuously deposited and from which the deposit is continuouslystripped as the drum rotates. It also includes means by which thickeningof the edges of the deposit and plating of metal on those portions ofthe drum where a deposit is not desired are prevented. In theseparticulars, the new apparatus involves the principles disclosed in myco-pending application, Serial No. 622,171, filed July 13, 1932, but itis superior to the apparatus of I that application in that highercurrent densities may be employed and a greater output thus obtained,without any impairment of the quality of the product.

In the prior apparatus, the cathode drum is mounted so that a portion ofits cylindrical deposit surface is continuously immersed in theelectrolyte in a lead-lined tank and this drum is provided withcircumferential channels at its ends. Ports are formed through thebottoms of i the channels leading to the spaces at the ends of the drum,and the drum is provided with partition means for isolating the minorbodies of electrolyte at the ends of the drum from the main body ofelectrolyte in the tank. In order to prevent thickening of the edges ofthe deposit sheet and also to complete the isolation of the minor bodiesof electrolyte, endless belts are provided at the ends of the drum, eachbelt having a portion which closes the open end of that portion of 50its channel lying below the electrolyte level and also overlies the edgeof the deposit surface adjacent the channel. In each conned body ofelectrolyte at the end of the drum, there is a sub-cathode maintained ata potential lower than i that of the drum itself, and with this arrange.

ment, any current which flows from the anode and passes into theconfined bodies of electrolyte does not cause a deposition of metal onthe inner surfaces of the channels or on the ends of the drum but flowsat once to the sub-cathodes.

The use of the novel features referred to makes it possible to carry onthe production of sheets and foils in the prior apparatus over longperiods of time without interruption, and the deposit strips easily fromthe drum and is of substantially uniform thickness from edge to edge.But it has been found that when a cell of the prior construction isoperated at a voltage in excess of a particular value, current flowsfrom the anode to the tank lining and thence to the cathode andsub-cathodes. This results in a change in the electrical relationsbetween `the cathode and the sub-cathodes with the result that copper isdeposited upon the lining and 'also upon the inner surfaces of thechannels, the ends of thedrum, o

and the sub-cathodes. In such a cell which has a lead lining andcontains a lead anode, the voltage at which the lining enters thecircuit is about 3.4 volts, and the apparatus must therefore be operatedat a. voltage below 3.4 volts alg5 though considerably higher voltagesare desirable and could be us'ed butfor the flow of current to and fromthelining. In that apparatus, therefore, the advantages of employing alead lining,-

instead of a non-conductive lining of mastic, for

example, have been obtained at some sacrifice in the output rate.

In the prior apparatus, the isolation of the bodies of electrolyte atthe ends of the drum' has required the use yof two separate means,

namely, partition members mounted on the drum and contacting with thetank lining and belts which close the entrances to the circumferentialchannels. The partition means used in practice are strips of sheetrubber mounted on the ends 40 of the drum to form short cylinders withthe v free edge of each cylindrical partition member engaging the tanklining. While these expedients accomplish the desired purpose, I havefound that two separate means are not necessary,

and in the apparatus of the present application,

I have devised an end construction on the drum which makes it possibleto use a single means both for preventing thickening at the edges of thedeposit and for isolating the bodies of electrolyte .at the ends of thedrum. This means includes a belt at each end of the drum which contactswith the deposit surface and also with 'a plate mounted in the tankbetween the end QI the drum and the lining. By making this i plate ofinsulating material and of the proper size and shape, I have found thatit may be used for performing the further function of preventing ow ofcurrent from the anode through the lining to the cathode. Accordingly,the new apparatus is not only simpler than that of the prior applicationbut it permits the use of higher voltages in a tank having a conductivelining. The novel features of construction of the apparatus, therefore,make available the advantages of a lead lining without sacrifice inoutput rate.

For a better understanding of the invention, reference may be had to theaccompanying drawing, in which Figure 1 is a View in transverse verticalsection through the apparatus with the cathode shown in elevation;

Figure 2 is a longitudinal vertical section through the apparatus withthe cathode shown in elevation; l

Figure 3 is a sectional view through a portion of the drum andassociated parts; and

Figure 4 is a fragmentary end view of the drum illustrating amodication.

Referring now to the drawing, the apparatus is shown as including a tankI0 of any suitable material, the tank having a lead Ilining II. Mountedon suitable supports I2 in the bottom Vof the tank are anodes I3, these.anodes being' of curved form and having lugs I4 at their upper endswhich extend to the side Walls of the tank, with one lug of each anodemaking contact with a bus bar by which current is supplied to the anode.At their lower ends, the anodes are spaced apart to permit circulationof electrolyte, such circulation being promoted, if desired, by the useof air jets in accordance with standard practice.

The cathode I5 employed in the apparatus has the form of a drum mountedon a shaft I6 journaled in bearings I1 supported on the side Walls ofthe tank. The drum may be of any suitable construction, but preferablyit includes end plates I8 of copper and a cylindrical copper member I9providing the, curved surface. 'Ihe deposit surface is'formed by acontinuous layer 20 of lead mounted on the cylindrical member I9 andprojecting beyond the ends of -that member. 'I'he end plates ofthe drumare provided with a lead sheathing 2I, and at each end-of the drum andlying inward from the projecting edges of the cylindrical depositmember, there is a ring 22 of lead which has a radially projectingflange 23. This flange is separated from the end of the deposit member2U by'a circumferential channel 24 and the outer end of the flangeprovides an inclined supporting surface 25, the outer edge of which liesinward from the cylindrical surface of the deposit member 20. At shortintervals, ports 26 are formed through the ange lto lead from the bottomof the channel. Instead of employing a continuous circumferential angewith ports at each end of the drum as described, spaced lugs 21 may beused, as shown in Figure 4, each lug having an inclined supportingsurface at its outer end similar to that designated 25 in Figure 3.

The cathode drum is provided with any suitable means for makingelectrical connection therewith as, for example, it may have a disc 28on the end of shaft I6 which dips into mercury 29 in a cup 30 mounted onthe tank wall, the cup being connected in the electrical system in thedesired manner.

At each end of the drum is mounted a belt 3| which is trained aboutpulleys 32, suitably supported at' the top of the tank, and pulleys 33mounted within the tank below the level of the electrolyte. Each belt ispreferably a hollow rubber tube and it has a portion which lies incontact with the edge of the deposit surface of the drum and alsowiththe inclined surface 25 of the supporting means. The supportingmeans tend to force the belt toward the deposit surface so that the beltwill overlie the edge of the latter to a substantial extent andtheamount' of the overhang of the belt may be varied by varying the tensionon the belt. This can be accomlplished in any suitable manner as, forexample,

by varying the positions of the pulleys 32, the mounting wherefor beingadjustable for that purpose.

In order vto accomplish its purpose of isolating a body of electrolyteat the end of the drum from r the main body of electrolyte, that portionof each belt which contacts with the drum must also bear against astationary surface. Where high current densities are not desired, thebelt may engage the tank lining or an extension therefrom, but I preferto mount a plate 34 at each end of the drum to provide the surface withwhich the belt makes contact. The plates 34 are of insulating materialand preferably of glass, and they are spaced sumciently close to theends of the drum so that each belt is flattened throughout its contactwith the adjacent plate and leakage between the belt and plate isprevented. With this arrangement, each belt and plate serve to preventfree circulation of electrolyte in contact with one end of the drum, andby overlying the edge of the deposit surface, the belt reduces edgethickening. The-'supporting means 23 prevent the belt from entering thespace between the plate and the end of the cylindrical deposit member 20and also force the belt toward the deposit surface so as to make goodcontact With, and overlie the edge thereof.

The plates 34 are mounted on supports at the bottom of the tank and theyextend up above the electrolyte level and are of such a shape and sizeas to constitute ashield which masks the entire immersed portions of theends of the drum and the anodes from the tank lining. The supportingmeans for the plates include blocks 35, which may be of lead or othersuitable material and reston the tank bottom, and on top of each blockis a cylindrical member 36 which may be a short length of lead pipesecured rigidly to the block. Resting freely on each cylindrical member36 is a semi-cylindrical member 31 secured to the lower end of a plate38 which extends upwardly and has a slot i'n its upper edge in which thelower edge of the plate 34 is received. The supporting plate 38 mayswing about the cylindrical member 36 to a slight degree and thus adjustitself but it is heldin a generally vertical position by a strap member39 secured tothe tank wall and loosely enclosing the plate 38. Twosupports o'. the construction described areprovided for each glass plate34 and the upper' end of the plate is held in proper relation'to thedrum by means of rubber blocks 40 insertedv between the plate and tanklining. v

In each confined body of electrolyte between a plate 34 andv one end ofthe drum are mounteda pair of sub-cathode elements 4I, these subcathodesbeing plates of metal attached to metal straps 42 which extend over thetop of the glass plate and are held in position in any suitable manner.The sub-cathodes are connected in the electrical system so that they arecontinuously maintained at a potential lower than that of the maincathode, and as a consequence, any current which passes from the anodeand enters the confined body of electrolyte at either end of the 5 drum,by reason of. leakage of electrolyte past the belt, flows at once to asub-cathode and does not cause a deposit of metal on the end of thedrum.

With the apparatus described, a single means l at each end ofthe drumprevents thickening of the deposit along its edge and also prevents freecirculation in contact with the endof the drum, and by using rubberbelts and glass plates with which the belts contact, a highly eiectiveisolal tion of the minor bodies of electrolyte at the ends of the drumis obtained. At the same time, the contact of a rubber belt with itsglass plate develops little friction and wear on the belt since thesurface of the plate is smooth and con- 20 tinually wet by electrolyte,The glass plates not only serve to cooperate with the belts for thepurpose mentioned, but they also shield the ends of the drum so thatiiowv of current from the anodes through the tank lining to the drum is25 prevented. The use of the plates, accordingly,

permits voltages much higher than those heretofore permissible in alead-lined tank, and greater current densities can be .obtained than arepossible without the plates. The new apparatus is 30- accordingly moreeillcient than my prior apparatus because of the increased output ofdeposited metal that can be obtained. The new apparatus, therefore,affords all of the advantages of the old construction plus theadditional ad- 35l vantages above pointed out.

I claim:

l. Apparatus for electrodeposition which comprises a tank containing anelectrolyte, a portion at least of the inner surface of the tank in con-40 tact with the electrolyte being of electroconductive material, ananode in the tank supplying current to the electrolyte, a cathodemounted to have a portion immersed in the electrolyte and withdrawingcurrent therefrom, means 'in the 45 tank for preventing current fromflowing from the anode through said electroconductive material to saidcathode, means for preventing .free circulation of the electrolyte incontact with the ends of the cathode, and a sub-cathode at each 50 endof said cathode immersed in the electrolyte which contacts with saidend, said sub-cathode being maintained ata lowerk potential than saidcathode. l

2.,Apparatusfor electrodeposition which com- 55 prises atank containingan electrolyte,a portion at least of the inner surface of the tank incontact with the electrolyte being of electroconductive material, ananode in the tank supplying current to the electrolyte, a rotatingkdrumcathoo ode mounted to have a portion continuously immersed in theelectrolyte and withdrawing current therefrom, plates in the tank'at theends of the cathode for preventing flow of current from the anodethrough said electroconductlve 65 material to the cathode, meanscooperating with the plates to prevent free circulation of theelectrolyte in contact with the ends of the cathode, and' a sub-cathodeat each end of said drum between said end and the adjacent plate and im-70 mersed in the electrolyte which contacts: with said end, saidsub-cathode being maintained at a potential lower than that of saiddrum.

3. Apparatus for electrodeposition which comprises a tank containingelectrolyte, an anode 'f5 inthe tank. for supplying current to theelectrolyte, a rotating drum cathode mounted to have a portion ofitsdeposit surface continuously immersed in said electrolyte andwithdrawing from said electrolyte, means at each end of the cathode forpreventing free circulation of electrolyte in 5 contact 4with said end,each means including a member traveling with the cathode in contact witha deposit surface thereof, and a fiat surface spaced from the end of thecathode and engaged by said member and lying at an angle to the axis ofrotation of the cathode, and a subcathode immersed in the electrolyte ateach end of said drum in space between said end and the adjacent atsurface, said sub-cathode being immersed in the electrolyte andmaintained ata potential lower than that of said drum.

4. Apparatus for electrodeposition which comprises a tank containingelectrolyte, an anode in the tank for supplying current to theelectrolyte, a rotating drum cathode mounted to have a portion of itsdeposit surface continuously immersed in said electrolyte andwithdrawing current. from said electrolyte, means at each end of thecathode for preventing free circulation of electrolyte in contact withsaid end, each means including a member traveling with the cathode incontact with the deposit surface thereof, and a plate spaced from theend of the cathode and engaged by said member, and a sub-cathode at eachend of said drum between said end and the adjacent plate, saidsub-cathode being immersed in the electrolyte and maintained at apotential lower than that of said drum.

5. Apparatus vfor electrodeposition which comprises a tank containingelectrolyte, an anode in 35 the tank for supplying current to theelectrolyte, a rotating drum cathode mounted to have a portion of itsdeposit surface continuously immersed in said electrolyte andwithdrawing current from said electrolyte, means at each end of thecathode 40 for preventing free circulation of electrolyte in contactwith said end,'each means including an '.endless member having at leasta portion in contact with the deposit surface of the cathode andtraveling therewithand a platev spaced from the end of the cathode andengaged by said portion of the member, and a sub-cathode at each end ofsaid drum between saidend andthe adjacent plate, said sub-cathode beingimmersed inthe electrolyte and maintained at a potential lower than thatof said drum. i'

6. Apparatus for electrodeposition which comprises a tank containingelectrolyte, k,an anode in the tank for supplying current, to theelectrolyte, a rotating drum cathode mounted to have a portion of itsdeposit surface continuously immersed in said electrolyte andwithdrawing current from said electrolyte, means at each end of thecathode for .preventing .free circulation of -electrolyte in contactwith said end, each means including a rubber belt having at least aportion in contact with the deposit surface `oi' the cathode immersed inthe electrolyte and traveling therewith, and a plate mounted inthe tankat the end of the cathode and having one face engaged by the belt, and asub-cathode at each end of the drum between said end and the adjacentplate, said sub-cathode being immersed in the electrolyte and maintainedat a potential .lower than that ofsaid drum. 70

il. In vapparatus for electrodeposition, the combination of a tankcontaining electrolyte, an anode in -the tank supplying current to theelectrolyte, a rotating drum cathode mounted to have a portion of itscylindrical deposit surface continuously immersed in the electrolyte andwithdrawing current therefrom, an endless member at each end of the drumand having at least a portion in contact with the deposit surface of the-drum and traveling therewith, and means on the drum for supporting themember, saidl means having surfaces engaging said member and lyinginward from the deposit surface.

8. Apparatus for electrodeposition which comprises a tank containingelectrolyte. an anode in the tank supplying current to the electrolyte,a rotating drum cathode mounted to have a-portion of its cylindricaldeposit surface continuously immersed in the electrolyte and withdrawingcurrent therefrom, a belt at each end of the drum having at least aportion in contact with the deposit surface of the drum and travelingtherewith, means at the ends of the drum for supporting the belts, saidmeans engaging portions of the belts inward from the deposit surface,and flat surfaces in the tank spaced from each end of the drum and lyingat an angle to the axis of rotation of the drum, each surface beingengaged by one of said belts.

9. Apparatus for electrodeposition which comprises a tank containingelectrolyte, an anode in the tank supplying current to the electrolyte,`a rotating drum cathode mounted to have a portion of its cylindricaldeposit surface continuously immersed in the electrolyte and withdrawingcurrent therefrom, a belt at each end of the drum having at least aportion in contact with the deposit surface of the drum and travelingvtherewith, a circumferential supporting member at each end of the drumfor supporting a belt, a plate in the tank at each end of the drum, eachplate being engaged by a belt, and a sub-cathode at each end of the drumimmersed in the electrolyte between -said end and the adjacent plate,said sub-I cathode being'maintained at a potential lower than that ofsaid drum.

10. Apparatus for electrodeposition which comprises a tank containingelectrolyte, an anode in the tank supplying current to the electrolyte,a rotating drum cathode mounted to have a portion of its cylindricaldeposit surface continuously immersed in the electrolyte and withdrawingcurrent therefrom, a belt at each end of the drum having at least aportion in contact with the deposit surface of the drum and travelingtherewith, a plurality of lugs arranged circumferentially at each end ofthe drum for supporting a belt, a plate in the tank at each end of thedrum, each plate being engaged by a belt, anda subcathode at each end ofthe drum immersed in the electrolyte between said end and the adjacentplate, said sub-cathode being maintained at a potential lower than thatof said drum.

11. Apparatus for electrodeposition which comprises a lead-lined tankcontaining electrolyte,

I an anode in the tank supplying, current to the electrolyte, a rotatingcathode drum having a cylindrical deposit surface, a portion of which iscontinuously immersed in the electrolyte andl lining to the drum, a pairof belts, one at'each means for the belts mounted on the drum and spacedfrom the deposit surface.

12. In an electrolytic tank, the combination of a rotating drum cathodehaving a cylindrical deposit surface, circumferentially disposedsupporting means at the ends of the drum having inclined supportingsurfaces lying inward from the deposit surface, and a pair of belts oneat each end of the drum, said belts having portions supported by saidsupporting means and in contact with said supporting surfaces.

13. In apparatus for electrodeposition, the combination of anelectrolytic tank, a rotating drum cathode having a cylindrical depositsurface a portion of which is continuously immersed in the electrolytein the tank, a pair of plates supported from beneath in the tankyadjacent the ends of the drum, a pair of members one at each end of thedrum each member having a portion engaging the deposit surface of thedrum and traveling therewith and also engaging the adjacent plate, and asub-cathode immersed lin the electrolyte at each end of said drum andlying between said end and the adjacent plate, said sub-cathode beingmaintained at a potentiallower than that of said drum.

14. In apparatus for electrodeposition, the combination of anelectrolytic tank, a rotating drum cathode having a cylindrical depositsurface, a portion of which is continuously immersed in the electrolytein the tank, circumferential supportv ing means at the ends of the drum,a smoothsurfaced plate at each end of the drum, said plate beingsupported from beneath in the tank and extending from below the lowestpart of said drum toabove the level of the electrolyte', an endlessrubber belt at each end of the drum, said beltengaging the immersedportion of the deposit surface and traveling therewith and also bearingagainst the .surface of the adjacent plate, said belt being in partsupported by one of said circumferential `supporting means, and. asubcathode immersed in the electrolyte at each end of the drum betweensaid end and the adjacent plate, said sub-cathode being maintained at apotential lower than that of said drum.

15. In apparatusfor electrodeposition, a drum cathode having acylindrical deposit surface, supporting members at the ends of the`drum,each member having a working surfaceflying inward and spaced from thedeposit surface`and inclined inward and toward said deposit surface, anda pair of endless belts one at each end of the drum,

each belt having a portion supported by the worki current to theelectrolyte,a rotating drum cathode mounted to have a portioncontinuously immersed in the electrolyte and withdrawing currenttherefrom, a sub-cathode mounted in the tank at each end of the drum andmaintained at a potential lower than that of the drum, plates in thetank at the ends of the drum for preventing iiow of current from theanode through said electroconductive material to the drum andsubcathodes, and means cooperating with the plates to confine minorbodies of electrolyte at the ends of the drum, said minor bodies ofelectrolyte being in contact with the ends of the drum, the subcathodes,and thinner surface of the tank.

CHARLES E. YATES.

